Let B be the point upto which the weighted glass tube is immersed in the liquid such that
l = 20 cm = 0.20 m.
Applying the law of floating, weight of tube = weight of the liquid displaced = upthrust
∴ mg = (Al)ρg
where m is the mass of the tube, A is crosssectional area of the tube and ρ is the density of liquid.